Second message design consideration for two-step random access chanel procedure

ABSTRACT

Certain aspects of the present disclosure relate to wireless communications, and more particularly, to transmission of a physical uplink control channel (PUCCH) transmission to acknowledge a second message of a two-step random access channel (RACH) procedure.

CROSS REFERENCE TO RELATED APPLICATION

This application hereby claims priority under 35 U.S.C. § 119 to pendingU.S. Provisional Patent Application No. 62/908,534, filed on Sep. 30,2019, the contents of which are incorporated herein in their entirety.

FIELD OF THE DISCLOSURE

Aspects of the present disclosure relate to wireless communications, andmore particularly, to transmission of a physical uplink control channel(PUCCH) transmission to acknowledge a second message of a two-steprandom access channel (RACH) procedure.

DESCRIPTION OF RELATED ART

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,broadcasts, etc. These wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power, etc.). Examples of such multiple-access systems include3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)systems, LTE Advanced (LTE-A) systems, code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems, to name a few.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. New radio (e.g., 5G NR) is an exampleof an emerging telecommunication standard. NR is a set of enhancementsto the LTE mobile standard promulgated by 3GPP. NR is designed to bettersupport mobile broadband Internet access by improving spectralefficiency, lowering costs, improving services, making use of newspectrum, and better integrating with other open standards using OFDMAwith a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL).To these ends, NR supports beamforming, multiple-input multiple-output(MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues toincrease, there exists a need for further improvements in NR and LTEtechnology. Preferably, these improvements should be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure may provide advantages, such as improvedreliability of message decoding and reduced complexity of blinddecoding.

Certain aspects provide a method for wireless communication by a userequipment (UE). The method generally includes transmitting a preamblesequence and a physical uplink shared channel (PUSCH) in a firsttransmission of a two-step random access channel (RACH) procedure,detecting a physical downlink control channel (PDCCH) transmission in asecond transmission of the two-step RACH procedure, the PDCCH indicatingresources to monitor for a physical downlink shared channel (PDSCH)transmission in the second transmission, determining at least onespatial domain transmission filter parameter for a physical uplinkcontrol channel (PUCCH) transmission providing acknowledgment feedbackfor the PDSCH transmission, and transmitting the PUCCH using thedetermined spatial domain transmission filter.

Certain aspects provide a method for wireless communication by a userequipment (UE). The method generally includes transmitting a preamblesequence and a physical uplink shared channel (PUSCH) in a firsttransmission of a two-step random access channel (RACH) procedure,detecting a physical downlink control channel (PDCCH) transmission in asecond transmission of the two-step RACH procedure, the PDCCH indicatingresources to monitor for a physical downlink shared channel (PDSCH)transmission in the second transmission, determining at least one of anumerology, bandwidth part (BWP), or waveform for a physical uplinkcontrol channel (PUCCH) transmission providing acknowledgment feedbackfor the PDSCH transmission, and transmitting the PUCCH using thedetermined numerology, BWP, or waveform.

Certain aspects provide a method for wireless communication by a userequipment (UE). The method generally includes transmitting a preamblesequence and a physical uplink shared channel (PUSCH) in a firsttransmission of a two-step random access channel (RACH) procedure,determining at least one characteristic for a physical downlink controlchannel (PDCCH) transmission in a second transmission of the two-stepRACH procedure, the PDCCH indicating resources to monitor for a physicaldownlink shared channel (PDSCH) transmission in the second transmission,and monitoring for the PDCCH transmission in the second transmissionbased on the determined characteristic.

Certain aspects provide a method for wireless communication by a userequipment (UE). The method generally includes transmitting a preamblesequence and a physical uplink shared channel (PUSCH) in a firsttransmission of a two-step random access channel (RACH) procedure,detecting a physical downlink control channel (PDCCH) transmission in asecond transmission of the two-step RACH procedure, the PDCCH indicatingresources to monitor for a physical downlink shared channel (PDSCH)transmission in the second transmission, determining at least one of aspatial domain transmission filter parameter, a numerology, a bandwidthpart (BWP), or a waveform for a physical uplink control channel (PUCCH)transmission providing acknowledgment feedback for the PDSCHtransmission, and transmitting the PUCCH using the determined spatialdomain transmission filter parameter, the determined numerology, thedetermined bandwidth part (BWP), or the determined waveform.

Certain aspects provide a user equipment (UE). The UE generally includesa transmitter configured to transmit a preamble sequence and a physicaluplink shared channel (PUSCH) in a first transmission of a two-steprandom access channel (RACH) procedure, at least one processor, and amemory coupled to the processor, wherein: the memory stores codesexecutable by the at least one processor to detect a physical downlinkcontrol channel (PDCCH) transmission in a second transmission of thetwo-step RACH procedure, the PDCCH indicating resources to monitor for aphysical downlink shared channel (PDSCH) transmission in the secondtransmission and determine at least one of a spatial domain transmissionfilter parameter, a numerology, a bandwidth part (BWP), or a waveformfor a physical uplink control channel (PUCCH) transmission providingacknowledgment feedback for the PDSCH transmission, and the transmitteris further configured to transmit the PUCCH using the determined spatialdomain transmission filter parameter, the determined numerology, thedetermined bandwidth part (BWP), or the determined waveform.

Aspects of the present disclosure provide means for, apparatus,processors, and computer-readable mediums for performing the methodsdescribed herein.

Aspects of the present disclosure provide means for, apparatus,processors, and computer-readable mediums for performing techniques andmethods that may be complementary to the operations by the UE describedherein, for example, by a BS.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe appended drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the drawings. It is to be noted, however, thatthe appended drawings illustrate only certain typical aspects of thisdisclosure and are therefore not to be considered limiting of its scope,for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an exampletelecommunications system, in accordance with certain aspects of thepresent disclosure.

FIG. 2 is a block diagram illustrating an example architecture of adistributed radio access network (RAN), in accordance with certainaspects of the present disclosure.

FIG. 3 is a block diagram showing examples for implementing acommunication protocol stack in the example RAN architecture, inaccordance with certain aspects of the present disclosure.

FIG. 4 is a block diagram conceptually illustrating a design of anexample base station (BS) and user equipment (UE), in accordance withcertain aspects of the present disclosure.

FIG. 5 illustrates an example system architecture for interworkingbetween a 5G System (5GS) and an evolved universal mobiletelecommunication system network (E-UTRAN) system, in accordance withcertain aspects of the present disclosure.

FIG. 6 illustrates an example of a frame format for a telecommunicationsystem, in accordance with certain aspects of the present disclosure.

FIG. 7 is a timing diagram illustrating an example four-step RACHprocedure, in accordance with certain aspects of the present disclosure.

FIG. 8 is a timing diagram illustrating an example two-step RACHprocedure, in accordance with certain aspects of the present disclosure.

FIG. 9 summarizes example content of messages of s two-step RACHprocedure, in accordance with certain aspects of the present disclosure.

FIG. 10A is a timing diagram illustrating additional details of anexample two-step RACH procedure, in accordance with certain aspects ofthe present disclosure.

FIG. 10B illustrates additional details of an example of a msgAtransmission occasion of a two-step RACH procedure, in accordance withcertain aspects of the present disclosure.

FIG. 11 is a flow diagram illustrating example operations for wirelesscommunication by a UE, in accordance with certain aspects of the presentdisclosure.

FIG. 12 is a flow diagram illustrating example operations for wirelesscommunication by a UE, in accordance with certain aspects of the presentdisclosure.

FIG. 13 is a flow diagram illustrating example operations for wirelesscommunication by a UE, in accordance with certain aspects of the presentdisclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in one aspectmay be beneficially utilized on other aspects without specificrecitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processingsystems, and computer readable mediums for processing and transmitting aphysical uplink control channel (PUCCH), for example, a PUCCH used toacknowledge a second message (e.g., msgB) transmission of a two-stepRACH procedure.

The following description provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate. Forinstance, the methods described may be performed in an order differentfrom that described, and various steps may be added, omitted, orcombined. Also, features described with respect to some examples may becombined in some other examples. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition to,or other than, the various aspects of the disclosure set forth herein.It should be understood that any aspect of the disclosure disclosedherein may be embodied by one or more elements of a claim. The word“exemplary” is used herein to mean “serving as an example, instance, orillustration.” Any aspect described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otheraspects.

The techniques described herein may be used for various wirelesscommunication technologies, such as LTE, CDMA, TDMA, FDMA, OFDMA,SC-FDMA and other networks. The terms “network” and “system” are oftenused interchangeably. A CDMA network may implement a radio technologysuch as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRAincludes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implementa radio technology such as Global System for Mobile Communications(GSM). An OFDMA network may implement a radio technology such as NR(e.g. 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRAand E-UTRA are part of Universal Mobile Telecommunication System (UMTS).

New Radio (NR) is an emerging wireless communications technology underdevelopment in conjunction with the 5G Technology Forum (5GTF). 3GPPLong Term Evolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTSthat use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies. For clarity, while aspects may be describedherein using terminology commonly associated with 3G and/or 4G wirelesstechnologies, aspects of the present disclosure can be applied in othergeneration-based communication systems, such as 5G and later, includingNR technologies.

New radio (NR) access (e.g., 5G technology) may support various wirelesscommunication services, such as enhanced mobile broadband (eMBB)targeting wide bandwidth (e.g., 80 MHz or beyond), millimeter wave (mmW)targeting high carrier frequency (e.g., 25 GHz or beyond), massivemachine type communications MTC (mMTC) targeting non-backward compatibleMTC techniques, and/or mission critical targeting ultra-reliablelow-latency communications (URLLC). These services may include latencyand reliability requirements. These services may also have differenttransmission time intervals (TTI) to meet respective quality of service(QoS) requirements. In addition, these services may co-exist in the samesubframe.

Example Wireless Communications System

FIG. 1 illustrates an example wireless communication network 100 inwhich aspects of the present disclosure may be performed. For example, aUE 120 may be configured to perform operations 1100 of FIG. 11,operations 1200 of FIG. 12, and/or operations 1300 of FIG. 13, toprocess and/or acknowledge transmissions of a two-step RACH procedure.

As illustrated in FIG. 1, the wireless communication network 100 mayinclude a number of base stations (BSs) 110 and other network entities.A BS may be a station that communicates with user equipments (UEs). EachBS 110 may provide communication coverage for a particular geographicarea. In 3GPP, the term “cell” can refer to a coverage area of a Node B(NB) and/or a NB subsystem serving this coverage area, depending on thecontext in which the term is used. In NR systems, the term “cell” andnext generation NodeB (gNB or gNodeB), NR BS, 5G NB, access point (AP),or transmission reception point (TRP) may be interchangeable. In someexamples, a cell may not necessarily be stationary, and the geographicarea of the cell may move according to the location of a mobile BS. Insome examples, the base stations may be interconnected to one anotherand/or to one or more other base stations or network nodes (not shown)in wireless communication network 100 through various types of backhaulinterfaces, such as a direct physical connection, a wireless connection,a virtual network, or the like using any suitable transport network.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a subcarrier, afrequency channel, a tone, a subband, etc. Each frequency may support asingle RAT in a given geographic area in order to avoid interferencebetween wireless networks of different RATs. In some cases, NR or 5G RATnetworks may be deployed.

A BS may provide communication coverage for a macro cell, a pico cell, afemto cell, and/or other types of cells. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having an association with the femto cell(e.g., UEs in a Closed Subscriber Group (CSG), UEs for users in thehome, etc.). A BS for a macro cell may be referred to as a macro BS. ABS for a pico cell may be referred to as a pico BS. A BS for a femtocell may be referred to as a femto BS or a home BS. In the example shownin FIG. 1, the BSs 110 a, 110 b and 110 c may be macro BSs for the macrocells 102 a, 102 b and 102 c, respectively. The BS 110 x may be a picoBS for a pico cell 102 x. The BSs 110 y and 110 z may be femto BSs forthe femto cells 102 y and 102 z, respectively. ABS may support one ormultiple (e.g., three) cells.

Wireless communication network 100 may also include relay stations. Arelay station is a station that receives a transmission of data and/orother information from an upstream station (e.g., a BS or a UE) andsends a transmission of the data and/or other information to adownstream station (e.g., a UE or a BS). A relay station may also be aUE that relays transmissions for other UEs. In the example shown in FIG.1, a relay station 110 r may communicate with the BS 110 a and a UE 120r in order to facilitate communication between the BS 110 a and the UE120 r. A relay station may also be referred to as a relay BS, a relay,etc.

Wireless communication network 100 may be a heterogeneous network thatincludes BSs of different types, e.g., macro BS, pico BS, femto BS,relays, etc. These different types of BSs may have different transmitpower levels, different coverage areas, and different impact oninterference in the wireless communication network 100. For example,macro BS may have a high transmit power level (e.g., 20 Watts) whereaspico BS, femto BS, and relays may have a lower transmit power level(e.g., 1 Watt).

Wireless communication network 100 may support synchronous orasynchronous operation. For synchronous operation, the BSs may havesimilar frame timing, and transmissions from different BSs may beapproximately aligned in time. For asynchronous operation, the BSs mayhave different frame timing, and transmissions from different BSs maynot be aligned in time. The techniques described herein may be used forboth synchronous and asynchronous operation.

A network controller 130 may couple to a set of BSs and providecoordination and control for these BSs. The network controller 130 maycommunicate with the BSs 110 via a backhaul. The BSs 110 may alsocommunicate with one another (e.g., directly or indirectly) via wirelessor wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout thewireless communication network 100, and each UE may be stationary ormobile. A UE may also be referred to as a mobile station, a terminal, anaccess terminal, a subscriber unit, a station, a Customer PremisesEquipment (CPE), a cellular phone, a smart phone, a personal digitalassistant (PDA), a wireless modem, a wireless communication device, ahandheld device, a laptop computer, a cordless phone, a wireless localloop (WLL) station, a tablet computer, a camera, a gaming device, anetbook, a smartbook, an ultrabook, an appliance, a medical device ormedical equipment, a biometric sensor/device, a wearable device such asa smart watch, smart clothing, smart glasses, a smart wrist band, smartjewelry (e.g., a smart ring, a smart bracelet, etc.), an entertainmentdevice (e.g., a music device, a video device, a satellite radio, etc.),a vehicular component or sensor, a smart meter/sensor, industrialmanufacturing equipment, a global positioning system device, or anyother suitable device that is configured to communicate via a wirelessor wired medium. Some UEs may be considered machine-type communication(MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include,for example, robots, drones, remote devices, sensors, meters, monitors,location tags, etc., that may communicate with a BS, another device(e.g., remote device), or some other entity. A wireless node mayprovide, for example, connectivity for or to a network (e.g., a widearea network such as Internet or a cellular network) via a wired orwireless communication link. Some UEs may be consideredInternet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT)devices.

Certain wireless networks (e.g., LTE) utilize orthogonal frequencydivision multiplexing (OFDM) on the downlink and single-carrierfrequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDMpartition the system bandwidth into multiple (K) orthogonal subcarriers,which are also commonly referred to as tones, bins, etc. Each subcarriermay be modulated with data. In general, modulation symbols are sent inthe frequency domain with OFDM and in the time domain with SC-FDM. Thespacing between adjacent subcarriers may be fixed, and the total numberof subcarriers (K) may be dependent on the system bandwidth. Forexample, the spacing of the subcarriers may be 15 kHz and the minimumresource allocation (called a “resource block” (RB)) may be 12subcarriers (or 180 kHz). Consequently, the nominal Fast FourierTransfer (FFT) size may be equal to 128, 256, 512, 1024 or 2048 forsystem bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz),respectively. The system bandwidth may also be partitioned intosubbands. For example, a subband may cover 1.08 MHz (i.e., 6 resourceblocks), and there may be 1, 2, 4, 8, or 16 subbands for systembandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR. NR may utilizeOFDM with a CP on the uplink and downlink and include support forhalf-duplex operation using TDD. Beamforming may be supported and beamdirection may be dynamically configured. MIMO transmissions withprecoding may also be supported. MIMO configurations in the DL maysupport up to 8 transmit antennas with multi-layer DL transmissions upto 8 streams and up to 2 streams per UE. Multi-layer transmissions withup to 2 streams per UE may be supported. Aggregation of multiple cellsmay be supported with up to 8 serving cells.

In some examples, access to the air interface may be scheduled. Ascheduling entity (e.g., a BS) allocates resources for communicationamong some or all devices and equipment within its service area or cell.The scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity. Base stations arenot the only entities that may function as a scheduling entity. In someexamples, a UE may function as a scheduling entity and may scheduleresources for one or more subordinate entities (e.g., one or more otherUEs), and the other UEs may utilize the resources scheduled by the UEfor wireless communication. In some examples, a UE may function as ascheduling entity in a peer-to-peer (P2P) network, and/or in a meshnetwork. In a mesh network example, UEs may communicate directly withone another in addition to communicating with a scheduling entity.

In FIG. 1, a solid line with double arrows indicates desiredtransmissions between a UE and a serving BS, which is a BS designated toserve the UE on the downlink and/or uplink. A finely dashed line withdouble arrows indicates interfering transmissions between a UE and a BS.

FIG. 2 illustrates an example architecture of a distributed Radio AccessNetwork (RAN) 200, which may be implemented in the wirelesscommunication network 100 illustrated in FIG. 1. As shown in FIG. 2, thedistributed RAN includes Core Network (CN) 202 and Access Node 208.

The CN 202 may host core network functions. CN 202 may be centrallydeployed. CN 202 functionality may be offloaded (e.g., to advancedwireless services (AWS)), in an effort to handle peak capacity. The CN202 may include the Access and Mobility Management Function (AMF) 204and User Plane Function (UPF) 206. The AMF 204 and UPF 206 may performone or more of the core network functions.

The AN 208 may communicate with the CN 202 (e.g., via a backhaulinterface). The AN 208 may communicate with the AMF 204 via an N2 (e.g.,NG-C) interface. The AN 208 may communicate with the UPF 208 via an N3(e.g., NG-U) interface. The AN 208 may include a central unit-controlplane (CU-CP) 210, one or more central unit-user plane (CU-UPs) 212, oneor more distributed units (DUs) 214-218, and one or more Antenna/RemoteRadio Units (AU/RRUs) 220-224. The CUs and DUs may also be referred toas gNB-CU and gNB-DU, respectively. One or more components of the AN 208may be implemented in a gNB 226. The AN 208 may communicate with one ormore neighboring gNBs.

The CU-CP 210 may be connected to one or more of the DUs 214-218. TheCU-CP 210 and DUs 214-218 may be connected via a F1-C interface. Asshown in FIG. 2, the CU-CP 210 may be connected to multiple DUs, but theDUs may be connected to only one CU-CP. Although FIG. 2 only illustratesone CU-UP 212, the AN 208 may include multiple CU-UPs. The CU-CP 210selects the appropriate CU-UP(s) for requested services (e.g., for aUE).

The CU-UP(s) 212 may be connected to the CU-CP 210. For example, theDU-UP(s) 212 and the CU-CP 210 may be connected via an E1 interface. TheCU-CP(s) 212 may connected to one or more of the DUs 214-218. TheCU-UP(s) 212 and DUs 214-218 may be connected via a F1-U interface. Asshown in FIG. 2, the CU-CP 210 may be connected to multiple CU-UPs, butthe CU-UPs may be connected to only one CU-CP.

A DU, such as DUs 214, 216, and/or 218, may host one or more TRP(s)(transmit/receive points, which may include an Edge Node (EN), an EdgeUnit (EU), a Radio Head (RH), a Smart Radio Head (SRH), or the like). ADU may be located at edges of the network with radio frequency (RF)functionality. A DU may be connected to multiple CU-UPs that areconnected to (e.g., under the control of) the same CU-CP (e.g., for RANsharing, radio as a service (RaaS), and service specific deployments).DUs may be configured to individually (e.g., dynamic selection) orjointly (e.g., joint transmission) serve traffic to a UE. Each DU214-216 may be connected with one of AU/RRUs 220-224.

The CU-CP 210 may be connected to multiple DU(s) that are connected to(e.g., under control of) the same CU-UP 212. Connectivity between aCU-UP 212 and a DU may be established by the CU-CP 210. For example, theconnectivity between the CU-UP 212 and a DU may be established usingBearer Context Management functions. Data forwarding between CU-UP(s)212 may be via a Xn-U interface.

The distributed RAN 200 may support fronthauling solutions acrossdifferent deployment types. For example, the RAN 200 architecture may bebased on transmit network capabilities (e.g., bandwidth, latency, and/orjitter). The distributed RAN 200 may share features and/or componentswith LTE. For example, AN 208 may support dual connectivity with NR andmay share a common fronthaul for LTE and NR. The distributed RAN 200 mayenable cooperation between and among DUs 214-218, for example, via theCU-CP 212. An inter-DU interface may not be used.

Logical functions may be dynamically distributed in the distributed RAN200. As will be described in more detail with reference to FIG. 3, theRadio Resource Control (RRC) layer, Packet Data Convergence Protocol(PDCP) layer, Radio Link Control (RLC) layer, Medium Access Control(MAC) layer, Physical (PHY) layers, and/or Radio Frequency (RF) layersmay be adaptably placed, in the AN and/or UE.

FIG. 3 illustrates a diagram showing examples for implementing acommunications protocol stack 300 in a RAN (e.g., such as the RAN 200),according to aspects of the present disclosure. The illustratedcommunications protocol stack 300 may be implemented by devicesoperating in a wireless communication system, such as a 5G NR system(e.g., the wireless communication network 100). In various examples, thelayers of the protocol stack 300 may be implemented as separate modulesof software, portions of a processor or ASIC, portions of non-collocateddevices connected by a communications link, or various combinationsthereof. Collocated and non-collocated implementations may be used, forexample, in a protocol stack for a network access device or a UE. Asshown in FIG. 3, the system may support various services over one ormore protocols. One or more protocol layers of the protocol stack 300may be implemented by the AN and/or the UE.

As shown in FIG. 3, the protocol stack 300 is split in the AN (e.g., AN208 in FIG. 2). The RRC layer 305, PDCP layer 310, RLC layer 315, MAClayer 320, PHY layer 325, and RF layer 530 may be implemented by the AN.For example, the CU-CP (e.g., CU-CP 210 in FIG. 2) and the CU-UP e.g.,CU-UP 212 in FIG. 2) each may implement the RRC layer 305 and the PDCPlayer 310. A DU (e.g., DUs 214-218 in FIG. 2) may implement the RLClayer 315 and MAC layer 320. The AU/RRU (e.g., AU/RRUs 220-224 in FIG.2) may implement the PHY layer(s) 325 and the RF layer(s) 330. The PHYlayers 325 may include a high PHY layer and a low PHY layer.

The UE may implement the entire protocol stack 300 (e.g., the RRC layer305, the PDCP layer 310, the RLC layer 315, the MAC layer 320, the PHYlayer(s) 325, and the RF layer(s) 330).

FIG. 4 illustrates example components of BS 110 and UE 120 (as depictedin FIG. 1), which may be used to implement aspects of the presentdisclosure. For example, antennas 452, processors 466, 458, 464, and/orcontroller/processor 480 of the UE 120 may be configured to perform theoperations described with respect to FIGS. 11, 12, and/or 13.

At the BS 110, a transmit processor 420 may receive data from a datasource 412 and control information from a controller/processor 440. Thecontrol information may be for the physical broadcast channel (PBCH),physical control format indicator channel (PCFICH), physical hybrid ARQindicator channel (PHICH), physical downlink control channel (PDCCH),group common PDCCH (GC PDCCH), etc. The data may be for the physicaldownlink shared channel (PDSCH), etc. The processor 420 may process(e.g., encode and symbol map) the data and control information to obtaindata symbols and control symbols, respectively. The processor 420 mayalso generate reference symbols, e.g., for the primary synchronizationsignal (PSS), secondary synchronization signal (SSS), and cell-specificreference signal (CRS). A transmit (TX) multiple-input multiple-output(MIMO) processor 430 may perform spatial processing (e.g., precoding) onthe data symbols, the control symbols, and/or the reference symbols, ifapplicable, and may provide output symbol streams to the modulators(MODs) 432 a through 432 t. Each modulator 432 may process a respectiveoutput symbol stream (e.g., for OFDM, etc.) to obtain an output samplestream. Each modulator may further process (e.g., convert to analog,amplify, filter, and upconvert) the output sample stream to obtain adownlink signal. Downlink signals from modulators 432 a through 432 tmay be transmitted via the antennas 434 a through 434 t, respectively.

At the UE 120, the antennas 452 a through 452 r may receive the downlinksignals from the base station 110 and may provide received signals tothe demodulators (DEMODs) in transceivers 454 a through 454 r,respectively. Each demodulator 454 may condition (e.g., filter, amplify,downconvert, and digitize) a respective received signal to obtain inputsamples. Each demodulator may further process the input samples (e.g.,for OFDM, etc.) to obtain received symbols. A MIMO detector 456 mayobtain received symbols from all the demodulators 454 a through 454 r,perform MIMO detection on the received symbols if applicable, andprovide detected symbols. A receive processor 458 may process (e.g.,demodulate, deinterleave, and decode) the detected symbols, providedecoded data for the UE 120 to a data sink 460, and provide decodedcontrol information to a controller/processor 480.

On the uplink, at UE 120, a transmit processor 464 may receive andprocess data (e.g., for the physical uplink shared channel (PUSCH)) froma data source 462 and control information (e.g., for the physical uplinkcontrol channel (PUCCH) from the controller/processor 480. The transmitprocessor 464 may also generate reference symbols for a reference signal(e.g., for the sounding reference signal (SRS)). The symbols from thetransmit processor 464 may be precoded by a TX MIMO processor 466 ifapplicable, further processed by the demodulators in transceivers 454 athrough 454 r (e.g., for SC-FDM, etc.), and transmitted to the basestation 110. At the BS 110, the uplink signals from the UE 120 may bereceived by the antennas 434, processed by the modulators 432, detectedby a MIMO detector 436 if applicable, and further processed by a receiveprocessor 438 to obtain decoded data and control information sent by theUE 120. The receive processor 438 may provide the decoded data to a datasink 439 and the decoded control information to the controller/processor440.

The controllers/processors 440 and 480 may direct the operation at theBS 110 and the UE 120, respectively. The processor 440 and/or otherprocessors and modules at the BS 110 may perform or direct the executionof processes for the techniques described herein. The memories 442 and482 may store data and program codes for BS 110 and UE 120,respectively. A scheduler 444 may schedule UEs for data transmission onthe downlink and/or uplink.

FIG. 5 illustrates an example system architecture 500 for interworkingbetween 5GS (e.g., such as the distributed RAN 200) and E-UTRAN-EPC, inaccordance with certain aspects of the present disclosure. As shown inFIG. 5, the UE 502 may be served by separate RANs 504A and 504Bcontrolled by separate core networks 506A and 506B, where the RAN 504Aprovides E-UTRA services and RAN 504B provides 5G NR services. The UEmay operate under only one RAN/CN or both RANs/CNs at a time.

In LTE, the basic transmission time interval (TTI) or packet duration isthe 1 ms subframe. In NR, a subframe is still 1 ms, but the basic TTI isreferred to as a slot. A subframe contains a variable number of slots(e.g., 1, 2, 4, 8, 16, . . . slots) depending on the subcarrier spacing.The NR RB is 12 consecutive frequency subcarriers. NR may support a basesubcarrier spacing of 15 KHz and other subcarrier spacing may be definedwith respect to the base subcarrier spacing, for example, 30 kHz, 60kHz, 120 kHz, 240 kHz, etc. The symbol and slot lengths scale with thesubcarrier spacing. The CP length also depends on the subcarrierspacing.

FIG. 6 is a diagram showing an example of a frame format 600 for NR. Thetransmission timeline for each of the downlink and uplink may bepartitioned into units of radio frames. Each radio frame may have apredetermined duration (e.g., 10 ms) and may be partitioned into 10subframes, each of 1 ms, with indices of 0 through 9. Each subframe mayinclude a variable number of slots depending on the subcarrier spacing.Each slot may include a variable number of symbol periods (e.g., 7 or 14symbols) depending on the subcarrier spacing. The symbol periods in eachslot may be assigned indices. A mini-slot, which may be referred to as asub-slot structure, refers to a transmit time interval having a durationless than a slot (e.g., 2, 3, or 4 symbols).

Each symbol in a slot may indicate a link direction (e.g., DL, UL, orflexible) for data transmission and the link direction for each subframemay be dynamically switched. The link directions may be based on theslot format. Each slot may include DL/UL data as well as DL/UL controlinformation.

In NR, a synchronization signal (SS) block is transmitted. The SS blockincludes a PSS, a SSS, and a two symbol PBCH. The SS block can betransmitted in a fixed slot location, such as the symbols 0-3 as shownin FIG. 6. The PSS and SSS may be used by UEs for cell search andacquisition. The PSS may provide half-frame timing, the SS may providethe CP length and frame timing. The PSS and SSS may provide the cellidentity. The PBCH carries some basic system information, such asdownlink system bandwidth, timing information within radio frame, SSburst set periodicity, system frame number, etc. The SS blocks may beorganized into SS bursts to support beam sweeping. Further systeminformation such as, remaining minimum system information (RMSI), systeminformation blocks (SIBs), other system information (OSI) can betransmitted on a physical downlink shared channel (PDSCH) in certainsubframes. The SS block can be transmitted up to sixty-four times, forexample, with up to sixty-four different beam directions for mmW. The upto sixty-four transmissions of the SS block are referred to as the SSburst set. SS blocks in an SS burst set are transmitted in the samefrequency region, while SS blocks in different SS bursts sets can betransmitted at different frequency locations.

In some circumstances, two or more subordinate entities (e.g., UEs) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE1) to anothersubordinate entity (e.g., UE2) without relaying that communicationthrough the scheduling entity (e.g., UE or BS), even though thescheduling entity may be utilized for scheduling and/or controlpurposes. In some examples, the sidelink signals may be communicatedusing a licensed spectrum (unlike wireless local area networks, whichtypically use an unlicensed spectrum).

A UE may operate in various radio resource configurations, including aconfiguration associated with transmitting pilots using a dedicated setof resources (e.g., a radio resource control (RRC) dedicated state,etc.) or a configuration associated with transmitting pilots using acommon set of resources (e.g., an RRC common state, etc.). Whenoperating in the RRC dedicated state, the UE may select a dedicated setof resources for transmitting a pilot signal to a network. Whenoperating in the RRC common state, the UE may select a common set ofresources for transmitting a pilot signal to the network. In eithercase, a pilot signal transmitted by the UE may be received by one ormore network access devices, such as an AN, or a DU, or portionsthereof. Each receiving network access device may be configured toreceive and measure pilot signals transmitted on the common set ofresources, and also receive and measure pilot signals transmitted ondedicated sets of resources allocated to the UEs for which the networkaccess device is a member of a monitoring set of network access devicesfor the UE. One or more of the receiving network access devices, or a CUto which receiving network access device(s) transmit the measurements ofthe pilot signals, may use the measurements to identify serving cellsfor the UEs, or to initiate a change of serving cell for one or more ofthe UEs.

Example RACH Procedures

A random-access channel (RACH) is so named because it refers to awireless channel (medium) that may be shared by multiple UEs and used bythe UEs to (randomly) access the network for communications. Forexample, the RACH may be used for call setup and to access the networkfor data transmissions. In some cases, RACH may be used for initialaccess to a network when the UE switches from a radio resource control(RRC) connected idle mode to active mode, or when handing over in RRCconnected mode. Moreover, RACH may be used for downlink (DL) and/oruplink (UL) data arrival when the UE is in RRC idle or RRC inactivemodes, and when reestablishing a connection with the network.

FIG. 7 is a timing (or “call-flow”) diagram 700 illustrating an examplefour-step RACH procedure, in accordance with certain aspects of thepresent disclosure. A first message (MSG1) may be sent from the UE 120to BS 110 on the physical random access channel (PRACH). In this case,MSG1 may only include a RACH preamble. BS 110 may respond with a randomaccess response (RAR) message (MSG2) which may include the identifier(ID) of the RACH preamble, a timing advance (TA), an uplink grant, cellradio network temporary identifier (C-RNTI), and a back off indicator.MSG2 may include a PDCCH communication including control information fora following communication on the PDSCH, as illustrated. In response toMSG2, MSG3 is transmitted from the UE 120 to BS 110 on the PUSCH. MSG3may include one or more of a RRC connection request, a tracking areaupdate request, a system information request, a positioning fix orpositioning signal request, or a scheduling request. The BS 110 thenresponds with MSG 4 which may include a contention resolution message.

In some cases, to speed access, a two-step RACH procedure may besupported. As the name implies, the two-step RACH procedure mayeffectively “collapse” the four messages of the four-step RACH procedureinto two messages.

FIG. 8 is a timing diagram 800 illustrating an example two-step RACHprocedure, in accordance with certain aspects of the present disclosure.A first enhanced message (msgA) may be sent from the UE 120 to BS 110.In certain aspects, msgA includes some or all the information from MSG1and MSG3 from the four-step RACH procedure, effectively combining MSG1and MSG3. For example, msgA may include MSG1 and MSG3 multiplexedtogether such as using one of time-division multiplexing orfrequency-division multiplexing. In certain aspects, msgA includes aRACH preamble for random access and a payload. The msgA payload, forexample, may include the UE-ID and other signaling information (e.g.,buffer status report (BSR)) or scheduling request (SR). BS 110 mayrespond with a random access response (RAR) message (msgB) which mayeffectively combine MSG2 and MSG4 described above. For example, msgB mayinclude the ID of the RACH preamble, a timing advance (TA), a back offindicator, a contention resolution message, UL/DL grant, and transmitpower control (TPC) commands.

Example Design Considerations for 2-Step RACH Procedure

As noted above, in a two-step RACH procedure, the msgA may include aRACH preamble and a PUSCH (e.g., carrying a small data payload). Thetwo-step RACH procedure may have various use cases. Examples of such usecases include transition from RRC IDLE/INACTIVE state to RRC CONNECTEDstate, small data transmission for a UE in RRC IDLE/INACTIVE state, andhandover from a source cell to target cell in an RRC CONNECTED state.The two-step RACH may also be used for maintenance and/or recoverypurposes. For example, a UE in the RRC CONNECTED state may use thetwo-step RACH procedure to recover from UL synchronization loss.

FIG. 9 summarizes the content of messages exchanged as part of thetwo-step RACH process. As shown, the PUSCH (of msg A) may carry theequivalent of the conventional (four-step RACH) msg3 (e.g., RRC request,buffer status report, and the like) Use cases of 2-step RACH, as well asa small amount of data. PDSCH (of msgB) may carry equivalent offour-step RACH msg2 and msg3 contents. The UE may also send a PUCCH toacknowledge if/when the UE successfully receives a msgB transmission.

FIG. 10A is a timing diagram illustrating additional details of anexample two-step RACH procedure, in accordance with certain aspects ofthe present disclosure. As illustrated, a UE may initiate the first step(STEP 1) of a two-step RACH procedure after performing downlink (DL)synchronization, decoding system information (SI), and performingreference signal (RS) measurement (e.g., based on an SSB transmission)and/or RRC signaling if the UE is in a connected state.

As illustrated, the preamble and (PUSCH) payload of msgA may be sentsequentially. FIG. 10B illustrates additional details of example timingof the msgA preamble signal and PUSCH transmission. The gNB may processthe msgA preamble and payload, then perform the second step (STEP 2),sending the msgB PDCCH and PDSCH. Finally, if the UE successfullyreceives the msgB transmission, it may send a PUCCH as acknowledgment.If the UE does not receive the PDSCH transmission, it may not send thePUCCH to convey a negative acknowledgement.

Aspects of the present disclosure provide various techniques that mayhelp address various considerations regarding the msgB ACK PUCCH. Forexample, techniques presented herein may help with PUCCH transmissionbeam management, PUCCH numerology configuration, and/or bandwidth part(BWP) configuration for the PUCCH and/or MsgA PUSCH. Aspects of thepresent disclosure may also help with BWP configuration for msgB PDCCHand/or PDSCH, as well as MsgB PDCCH search space configuration.

FIG. 11 is a flow diagram illustrating example operations 1100 forwireless communication, in accordance with certain aspects of thepresent disclosure. The operations 1100 may be performed, for example,by a UE (e.g., such as a UE 120 a in the wireless communication network100).

Operations 1100 begin, at 1102, by transmitting a preamble sequence anda physical uplink shared channel (PUSCH) in a first transmission of atwo-step random access channel (RACH) procedure.

At 1104, the UE detects a physical downlink control channel (PDCCH)transmission in a second transmission of the two-step RACH procedure,the PDCCH indicating resources to monitor for a physical downlink sharedchannel (PDSCH) transmission in the second transmission.

At 1106, the UE determines at least one spatial domain transmissionfilter parameter for a physical uplink control channel (PUCCH)transmission providing acknowledgment feedback for the PDSCHtransmission. For example, the UE may determine a transmit beam to usefor transmitting the PUCCH.

At 1108, the UE transmits the PUCCH using the determined spatial domaintransmission filter. For example, the PUCCH may transmit the PUCCH usinga transmit beam determined at 1106.

In some cases, the UE may transmit the PUCCH using the same spatialdomain transmission filter (UL Tx beam) as for a previous transmission.For example, the UE may transmit the PUCCH using a UL Tx beam used totransmit a PUSCH transmission in MsgA (carrying MsgA payload). In thecase of a re-transmission, the UE may use the UL Tx beam of the mostrecent (latest) PUSCH (re)transmission before sending the PUCCH. In somecases, the UE may use a same UL Tx beam as used for a PRACH transmissionin MsgA (e.g., the MsgA preamble). In such cases, the UE may use thesame UL Tx beam used for the latest PRACH (re)transmission beforesending PUCCH.

In some cases, the gNB may configure the spatial domain transmissionfilter to be used for PUCCH. In such cases, the UE may report the beammeasurement (e.g., based on SS/PBCH block or CSI-RS) to the gNB in MsgAand the gNB may configure the UE with a Tx beam selected based on themeasurement report. In other cases, the UE may autonomously determinethe spatial domain transmission for PUCCH based on SS/PBCH block orCSI-RS beam measurement.

Regardless of how the UE determines the spatial domain transmissionfilter for the initial PUCCH transmission (e.g., according to any of theoptions above), the UE may adjust the spatial domain transmission filterbetween PUCCH re-transmission.

In some cases, the Tx beam selection for PUCCH may depend on one or moreother factors. For example, the Tx beam selection may be based on thespatial domain transmission filter used for transmission of at least oneof the preamble sequence or the PUSCH if the UE is in an RRC connectedidle or inactive state. As another example, the Tx beam selection may bebased on signaling, from a network entity (the gNB), indicating thespatial domain transmission filter for transmitting the PUCCH if the UEis in an RRC connected state.

In some cases, the Tx beam selection may be based on PUCCH format. Forexample, in one case, a UE may use PUCCH Format 0/1/4 only to multiplexHARQ ACK from multiple UEs, may use short PUCCH Format 0/2 only forlower latency (e.g., URLLC). In some cases, the UE may use PUCCH Format0 for RRC IDLE/INACTIVE UE, and PUCCH Format 2 for RRC CONNECTED UE. Insome cases, a UE may use any PUCCH Format, but with additionalconstraints on the length of PUCCH symbols (e.g., if long PUCCH formatis used, no more than 4 PUCCH symbols may be configured). In some cases,since PUCCH formats 0/1/2 support CP-OFDM, and formats 3/4 supportDFT-s-OFDM, the waveform of PUCCH may be similar to that of PUSCH.

As noted above, aspects of the present disclosure also providetechniques that may help with PUCCH numerology configuration, bandwidthpart (BWP) configuration, and/or waveform determination for the PUCCHand/or MsgA PUSCH.

FIG. 12 is a flow diagram illustrating example operations 1200 forwireless communication, in accordance with certain aspects of thepresent disclosure. The operations 1200 may be performed, for example,by a UE (e.g., such as a UE 120 a in the wireless communication network100).

Operations 1200 begin, at 1202, by transmitting a preamble sequence anda physical uplink shared channel (PUSCH) in a first transmission of atwo-step random access channel (RACH) procedure.

At 1204, the UE detects a physical downlink control channel (PDCCH)transmission in a second transmission of the two-step RACH procedure,the PDCCH indicating resources to monitor for a physical downlink sharedchannel (PDSCH) transmission in the second transmission.

At 1206, the UE determines at least one of a numerology, bandwidth part(BWP), or waveform for a physical uplink control channel (PUCCH)transmission providing acknowledgment feedback for the PDSCHtransmission.

At 1208, the UE transmits the PUCCH using the determined numerology,BWP, or waveform.

The numerology configuration of PUCCH can consider the various options.According to one option, the PUCCH numerology may be the same as thenumerology of the UL BWP configured for msgA transmission. According toanother option, the PUCCH numerology may be the same as the numerologyof MsgA preamble. In some cases, the gNB may configure whether the PUCCHnumerology is the same as the numerology of msgA preamble or thenumerology of UL BWP configured for msgA transmission. In some cases,the numerology of PUCCH may be explicitly configured for the UE (e.g.,signaled to the UE via SI or RRC signaling).

In some cases, PUCCH and MsgA may be transmitted using the same ULbandwidth part (BWP) configured for the latest MsgA transmission.

In some cases, in a same transmission occasion of msgB, PDCCH and PDSCH,the same numerology as DL BWP configured for MsgB PDCCH/PDSCH may beused. For different transmission occasions of msgB (e.g., for aretransmission of msgB), it may be left up to the network to configurethe numerology/BWP of PDCCH/PDSCH (for the retransmission). In thismanner, from one MsgB Tx occasion to another MsgB Tx occasion, the DLBWP for PDCCH/PDSCH can be reconfigured.

As noted above, aspects of the present disclosure may also help with BWPconfiguration for msgB PDCCH and/or PDSCH, as well as MsgB PDCCH searchspace configuration.

FIG. 13 is a flow diagram illustrating example operations 1300 forwireless communication, in accordance with certain aspects of thepresent disclosure. The operations 1300 may be performed, for example,by a UE (e.g., such as a UE 120 a in the wireless communication network100).

Operations 1300 begin, at 1302, by transmitting a preamble sequence anda physical uplink shared channel (PUSCH) in a first transmission of atwo-step random access channel (RACH) procedure.

At 1304, the UE detects at least one characteristic for a physicaldownlink control channel (PDCCH) transmission in a second transmissionof the two-step RACH procedure, the PDCCH indicating resources tomonitor for a physical downlink shared channel (PDSCH) transmission inthe second transmission.

At 1306, the UE monitors for the PDCCH transmission in the secondtransmission based on the determined characteristic.

In some cases, if a RACH occasion (RO) is shared by a group of RRCCONNECTED UEs attempting a 4-step RACH and 2-step RACH, the search spacefor msgB may be configured according various options. For example,according to a first option, the same PDCCH search space and same BWPmay be used for the 4-step RACH and the 2-step RACH. According to asecond option, different PDCCH search spaces, but the same BWP, may beused for the 4-step RACH and the 2-step RACH. According to a thirdoption, different BWPs and different PDCCH search spaces may be used forthe 4-step RACH and the 2-step RACH.

The techniques described herein may be used for various wirelesscommunication technologies, such as NR (e.g., 5G NR), 3GPP Long TermEvolution (LTE), LTE-Advanced (LTE-A), code division multiple access(CDMA), time division multiple access (TDMA), frequency divisionmultiple access (FDMA), orthogonal frequency division multiple access(OFDMA), single-carrier frequency division multiple access (SC-FDMA),time division synchronous code division multiple access (TD-SCDMA), andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA network may implement aradio technology such as Global System for Mobile Communications (GSM).An OFDMA network may implement a radio technology such as NR (e.g. 5GRA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA andE-UTRA are part of Universal Mobile Telecommunication System (UMTS). LTEand LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE,LTE-A and GSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). cdma2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). NR is an emerging wireless communications technologyunder development.

The techniques described herein may be used for the wireless networksand radio technologies mentioned above as well as other wirelessnetworks and radio technologies. For clarity, while aspects may bedescribed herein using terminology commonly associated with 3G, 4G,and/or 5G wireless technologies, aspects of the present disclosure canbe applied in other generation-based communication systems.

In 3GPP, the term “cell” can refer to a coverage area of a Node B (NB)and/or a NB subsystem serving this coverage area, depending on thecontext in which the term is used. In NR systems, the term “cell” andBS, next generation NodeB (gNB or gNodeB), access point (AP),distributed unit (DU), carrier, or transmission reception point (TRP)may be used interchangeably. A BS may provide communication coverage fora macro cell, a pico cell, a femto cell, and/or other types of cells. Amacro cell may cover a relatively large geographic area (e.g., severalkilometers in radius) and may allow unrestricted access by UEs withservice subscription. A pico cell may cover a relatively smallgeographic area and may allow unrestricted access by UEs with servicesubscription. A femto cell may cover a relatively small geographic area(e.g., a home) and may allow restricted access by UEs having anassociation with the femto cell (e.g., UEs in a Closed Subscriber Group(CSG), UEs for users in the home, etc.). A BS for a macro cell may bereferred to as a macro BS. A BS for a pico cell may be referred to as apico BS. A BS for a femto cell may be referred to as a femto BS or ahome BS.

A UE may also be referred to as a mobile station, a terminal, an accessterminal, a subscriber unit, a station, a Customer Premises Equipment(CPE), a cellular phone, a smart phone, a personal digital assistant(PDA), a wireless modem, a wireless communication device, a handhelddevice, a laptop computer, a cordless phone, a wireless local loop (WLL)station, a tablet computer, a camera, a gaming device, a netbook, asmartbook, an ultrabook, an appliance, a medical device or medicalequipment, a biometric sensor/device, a wearable device such as a smartwatch, smart clothing, smart glasses, a smart wrist band, smart jewelry(e.g., a smart ring, a smart bracelet, etc.), an entertainment device(e.g., a music device, a video device, a satellite radio, etc.), avehicular component or sensor, a smart meter/sensor, industrialmanufacturing equipment, a global positioning system device, or anyother suitable device that is configured to communicate via a wirelessor wired medium. Some UEs may be considered machine-type communication(MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include,for example, robots, drones, remote devices, sensors, meters, monitors,location tags, etc., that may communicate with a BS, another device(e.g., remote device), or some other entity. A wireless node mayprovide, for example, connectivity for or to a network (e.g., a widearea network such as Internet or a cellular network) via a wired orwireless communication link. Some UEs may be consideredInternet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT)devices.

Certain wireless networks (e.g., LTE) utilize orthogonal frequencydivision multiplexing (OFDM) on the downlink and single-carrierfrequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDMpartition the system bandwidth into multiple (K) orthogonal subcarriers,which are also commonly referred to as tones, bins, etc. Each subcarriermay be modulated with data. In general, modulation symbols are sent inthe frequency domain with OFDM and in the time domain with SC-FDM. Thespacing between adjacent subcarriers may be fixed, and the total numberof subcarriers (K) may be dependent on the system bandwidth. Forexample, the spacing of the subcarriers may be 15 kHz and the minimumresource allocation (called a “resource block” (RB)) may be 12subcarriers (or 180 kHz). Consequently, the nominal Fast FourierTransfer (FFT) size may be equal to 128, 256, 512, 1024 or 2048 forsystem bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz),respectively. The system bandwidth may also be partitioned intosubbands. For example, a subband may cover 1.08 MHz (e.g., 6 RBs), andthere may be 1, 2, 4, 8, or 16 subbands for system bandwidth of 1.25,2.5, 5, 10 or 20 MHz, respectively. In LTE, the basic transmission timeinterval (TTI) or packet duration is the 1 ms subframe.

NR may utilize OFDM with a CP on the uplink and downlink and includesupport for half-duplex operation using TDD. In NR, a subframe is still1 ms, but the basic TTI is referred to as a slot. A subframe contains avariable number of slots (e.g., 1, 2, 4, 8, 16, . . . slots) dependingon the subcarrier spacing. The NR RB is 12 consecutive frequencysubcarriers. NR may support a base subcarrier spacing of 15 KHz andother subcarrier spacing may be defined with respect to the basesubcarrier spacing, for example, 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc.The symbol and slot lengths scale with the subcarrier spacing. The CPlength also depends on the subcarrier spacing. Beamforming may besupported and beam direction may be dynamically configured. MIMOtransmissions with precoding may also be supported. In some examples,MIMO configurations in the DL may support up to 8 transmit antennas withmulti-layer DL transmissions up to 8 streams and up to 2 streams per UE.In some examples, multi-layer transmissions with up to 2 streams per UEmay be supported. Aggregation of multiple cells may be supported with upto 8 serving cells.

In some examples, access to the air interface may be scheduled. Ascheduling entity (e.g., a BS) allocates resources for communicationamong some or all devices and equipment within its service area or cell.The scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity. Base stations arenot the only entities that may function as a scheduling entity. In someexamples, a UE may function as a scheduling entity and may scheduleresources for one or more subordinate entities (e.g., one or more otherUEs), and the other UEs may utilize the resources scheduled by the UEfor wireless communication. In some examples, a UE may function as ascheduling entity in a peer-to-peer (P2P) network, and/or in a meshnetwork. In a mesh network example, UEs may communicate directly withone another in addition to communicating with a scheduling entity.

In some examples, two or more subordinate entities (e.g., UEs) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE1) to anothersubordinate entity (e.g., UE2) without relaying that communicationthrough the scheduling entity (e.g., UE or BS), even though thescheduling entity may be utilized for scheduling and/or controlpurposes. In some examples, the sidelink signals may be communicatedusing a licensed spectrum (unlike wireless local area networks, whichtypically use an unlicensed spectrum).

The methods disclosed herein comprise one or more steps or actions forachieving the methods. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed under the provisions of 35U.S.C. § 112(f) unless the element is expressly recited using the phrase“means for” or, in the case of a method claim, the element is recitedusing the phrase “step for.”

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a userterminal 120 (see FIG. 1), a user interface (e.g., keypad, display,mouse, joystick, etc.) may also be connected to the bus. The bus mayalso link various other circuits such as timing sources, peripherals,voltage regulators, power management circuits, and the like, which arewell known in the art, and therefore, will not be described any further.The processor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, ROM (ReadOnly Memory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein, for example, instructions for performing the operationsdescribed herein and illustrated in FIGS. 11, 12, and/or 13.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

1. A method for wireless communications by a user equipment (UE),comprising: transmitting a preamble sequence and a physical uplinkshared channel (PUSCH) in a first transmission of a two-step randomaccess channel (RACH) procedure; detecting a physical downlink controlchannel (PDCCH) transmission in a second transmission of the two-stepRACH procedure, the PDCCH indicating resources to monitor for a physicaldownlink shared channel (PDSCH) transmission in the second transmission;determining at least one of a spatial domain transmission filterparameter, a numerology, a bandwidth part (BWP), or a waveform for aphysical uplink control channel (PUCCH) transmission providingacknowledgment feedback for the PDSCH transmission; and transmitting thePUCCH using the determined spatial domain transmission filter parameter,the determined numerology, the determined bandwidth part (BWP), or thedetermined waveform.
 2. The method of claim 1, wherein the spatialdomain transmission filter parameter corresponds to a transmit beam. 3.The method of claim 1, wherein the determination is based on a spatialdomain transmission filter parameter used for transmission of at leastone of the preamble sequence or the PUSCH of the first transmission. 4.The method of claim 3, wherein: the preamble sequence and PUSCH of thefirst transmission may be re-transmitted at least once; and thedetermination is based on a spatial domain transmission filter parameterused for a latest re-transmission of at least one of the preamblesequence or the PUSCH of the first transmission.
 5. The method of claim1, wherein the determination is based on signaling, from a networkentity, indicating the spatial domain transmission filter parameter fortransmitting the PUCCH.
 6. The method of claim 5, further comprising:reporting downlink reference signal (RS) measurement to the networkentity, for use in selecting the spatial domain transmission filterparameter for transmitting the PUCCH.
 7. The method of claim 6, furthercomprising reporting the downlink RS measurement via the PUSCH of thefirst transmission.
 8. The method of claim 1, wherein the UE determinesthe spatial domain transmission filter parameter for transmitting thePUCCH based on downlink reference signal measurement.
 9. The method ofclaim 1, wherein: the PUCCH is re-transmitted at least once; and the UEadjusts the spatial domain transmission filter parameter used before there-transmission.
 10. The method of claim 1, wherein the determination isbased on a radio resource control (RRC) state of the UE.
 11. The methodof claim 10, wherein the determination is based on a spatial domaintransmission filter parameter used for transmission of at least one ofthe preamble sequence or the PUSCH if the UE is in an RRC connected idleor inactive state.
 12. The method of claim 10, wherein the determinationis based on signaling, from a network entity, indicating the spatialdomain transmission filter parameter for transmitting the PUCCH if theUE is in an RRC connected state.
 13. The method of claim 1, wherein thedetermination is based on a format of the PUCCH.
 14. The method of claim1, wherein the determination is based on a numerology of an uplink BWPconfigured for transmission of at least one of the preamble sequence orthe PUSCH of the first transmission.
 15. The method of claim 1, whereinthe determination is based on a numerology used for transmission of thepreamble sequence.
 16. The method of claim 1, wherein the determinationof the numerology, the bandwidth part (BWP), or the waveform is based onsignaling, from a network entity.
 17. The method of claim 16, whereinthe signaling indicates whether the numerology for the PUCCHtransmission is to be the same as a numerology used for transmission ofat least one of the preamble sequence or the PUSCH of the firsttransmission.
 18. The method of claim 16, wherein the signalingcomprises at least one of system information or radio resource control(RRC) signaling.
 19. The method of claim 1, wherein the determination ofthe waveform of the PUCCH is based on the waveform of the PUSCH of thefirst transmission.
 20. The method of claim 1, wherein: the preamblesequence and the PUSCH of the first transmission are re-transmitted atleast once; and the determination is to use an uplink BWP for the PUCCHtransmission as for a latest re-transmission of at least one of thepreamble sequence or the PUSCH of the first transmission.
 21. A methodfor wireless communications by a user equipment (UE), comprising:transmitting a preamble sequence and a physical uplink shared channel(PUSCH) in a first transmission of a two-step random access channel(RACH) procedure; determining at least one characteristic for a physicaldownlink control channel (PDCCH) transmission in a second transmissionof the two-step RACH procedure, the PDCCH indicating resources tomonitor for a physical downlink shared channel (PDSCH) transmission inthe second transmission; and monitoring for the PDCCH transmission inthe second transmission based on the determined characteristic.
 22. Themethod of claim 21, wherein the at least one characteristic comprises asearch space for the UE to monitor for the PDCCH transmission.
 23. Themethod of claim 22, wherein: a RACH occasion (RO) for transmitting thepreamble sequence is shared with an RO for a four-step RACH procedure;the at least one characteristic further comprises a bandwidth path (BWP)as used in the four-step RACH procedure; and the search space is thesame as a search space used in the four-step RACH procedure.
 24. A userequipment (UE), comprising: a transmitter configured to transmit apreamble sequence and a physical uplink shared channel (PUSCH) in afirst transmission of a two-step random access channel (RACH) procedure;at least one processor; and a memory coupled to the processor, wherein:the memory stores codes executable by the at least one processor to:detect a physical downlink control channel (PDCCH) transmission in asecond transmission of the two-step RACH procedure, the PDCCH indicatingresources to monitor for a physical downlink shared channel (PDSCH)transmission in the second transmission; and determine at least one of aspatial domain transmission filter parameter, a numerology, a bandwidthpart (BWP), or a waveform for a physical uplink control channel (PUCCH)transmission providing acknowledgment feedback for the PDSCHtransmission; and the transmitter is further configured to transmit thePUCCH using the determined spatial domain transmission filter parameter,the determined numerology, the determined bandwidth part (BWP), or thedetermined waveform.
 25. The UE of claim 24, wherein the spatial domaintransmission filter parameter corresponds to a transmit beam.
 26. The UEof claim 24, wherein the determination is based on a spatial domaintransmission filter parameter used for transmission of at least one ofthe preamble sequence or the PUSCH of the first transmission.
 27. The UEof claim 26, wherein: the preamble sequence and PUSCH of the firsttransmission may be re-transmitted at least once; and the determinationis based on a spatial domain transmission filter parameter used for alatest re-transmission of at least one of the preamble sequence or thePUSCH of the first transmission.
 28. The UE of claim 24, wherein thedetermination is based on a numerology of an uplink BWP configured fortransmission of at least one of the preamble sequence or the PUSCH ofthe first transmission.
 29. The UE of claim 24, wherein, at least oneof: the determination of the numerology, the bandwidth part (BWP), orthe waveform is based on signaling, from a network entity; or thesignaling indicates whether the numerology for the PUCCH transmission isto be the same as a numerology used for transmission of at least one ofthe preamble sequence or the PUSCH of the first transmission.
 30. The UEof claim 24, wherein: the preamble sequence and the PUSCH of the firsttransmission are re-transmitted at least once; and the determination isto use an uplink BWP for the PUCCH transmission as for a latestre-transmission of at least one of the preamble sequence or the PUSCH ofthe first transmission.